Douglas McCain, a Minnesotan who had been killed fighting alongside ISIS, was childhood best friends with another American who had joined an al Qaeda-linked terror group fighting in Somalia.

One of McCain's closest childhood friends was Troy Kastigar. Over a decade ago, Kastigar and McCain had shared an address, and the two graduated together from Robbinsdale Cooper High School in New Hope, Minnesota, in 1999.

Kastigar's story foreshadows McCain's own future radicalization and involvement with terrorist groups. He traveled to Somalia to join the al Qaeda-linked Al-Shabaab terrorist group in 2009, joining a multi-sided conflict involving the jihadist group, the Ethiopian military, and the country's Transitional Federal Government. Kastigar was killed in the same year.

While in Somalia, Kastigar starred in a propaganda video for Al-Shabaab in an attempt to lure other Americans into joining the group.

"If you guys only knew how much fun we have over here — this is the real Disneyland. Come here and join us," Kastigar said in the video.

Minnesota has a large Somali community, and a number of recruits for Al-Shabaab have come from the state. More than ten Minnesotans have gone to Somalia to join the terror organization.

Looking through McCain's Facebook profile, it seems that he became radicalized around the same time as Kastigar's death in Somalia.

In 2013, when McCain began to interact with ISIS supporters on Twitter, he changed his Facebook profile picture to a memorial image of Kastigar.

In the comments, McCain and his Facebook friend's praised Kastigar as a martyr and express their hopes that he was in heaven.

McCain may be the first American to have have died fighting for ISIS, but he is not the first to die fighting for jihadists in Syria. In May, an American from Florida became the first American suicide bomber in Syria's ongoing civil war.

The State Department told CNN on Tuesday that upwards of 100 Americans could now be fighting in Syria for a range of opposition groups.

State Department spokeswoman Jen Psaki has said that out of respect for McCain's family, there will be no additional comment from the U.S. government on his death.

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